1. Field of the Invention
The present invention relates to a novel and useful isocyanate prepolymer and a process for preparing the same. More particularly, the present invention relates to an isocyanate prepolymer for use in a hardener of two-component urethane resin, which is useful for paints, adhesives, and molding materials and processes for preparing the same. The isocyanate prepolymer are synthesized by a reaction between organic di-isocyanates and a relatively long chain unsaturated alcohol dimer such as oleyl alcohol dimer and/or a hydrogen addition product of the unsaturated alcohol dimer.
2. Prior Art
As flexible isocyanate prepolymers for use in hardeners of two-component urethane resin, so-called adduct-type isocyanate prepolymers prepared by addition reaction of organic di-isocyanate with polyether polyols such as polypropylene glycol are known. These kinds of isocyanate prepolymers, however, have an essential drawback with respect to their durability as the intramolecular ether bonds of the isocyanate prepolymers are vulnerable to oxidative deterioration.
Recently, another adduct-type isocyanate prepolymer, prepared by addition reaction of an organic di-isocyanate with a polyester diol, has been used.
Nevertheless, since this kind of isocyanate prepolymer is vulnerable to hydrolysis of the intramolecular ester bonds thereof, cleavage of the ester bonds is especially common. When the isocyanate prepolymers contact alkaline materials such as concrete and the like, the prepolymers have the same durability problem as described in the foregoing case since the ester bonds of the prepolymers are vulnerable to cleavage.
Various isocyanate prepolymers which have been used in a flexible hardener for use in two-component urethane resins have generally a disadvantage in their durability for practical use.